refactored send response workflow
refactored send response workflow

- added SendResponseEvent
- ResponseSender listen for an event
- first response sender that can send the response, stops propagation
- send response listener just triggers event, sends no response
- SendResponseEvent tracks which response headers and content were sent
- send response listener attaches default listeners (phpenvironmentresponse and consoleresponse, stream response sender is in progress)
- removed AbstractResponseSender

zendframework/zend-http,malinink/zend-http,Maks3w/zend-http,asgrim/zend-http,netroby/zend-http,weierophinney/zend-http